132 ' BYZANTINE CHURCHES CHAP.
the gallery" on the south of the south church are covered with cross-groined vaults without transverse arches. The wall of the south church, which shows in the south gallery, formed the original external wall of the building. It is divided into bays with arches in two and three orders of brick reveals, and with shallow niches on the broader piers.
The exterior of the two churches is very plain. On the west are shallow wall arcades in one order, on the south similar arcades in two orders. The northern side is inaccessible owing to the Turkish houses built against it.
On the east all the apses project boldly. The central apse of the south church has seven sides and shows the remains of a decoration of niches in two stories similar to that of the Pantokrator (p. 235) ; the other apses present three sides. The carved work on the window shafts is throughout good. An inscription commemorating the erection of the northern church is cut on a marble string-course which, when complete, ran across the whole eastern end, following the projecting sides of the apses. The letters are sunk and marked with drill holes.
Wulff is of opinion that the letters were originally filled in with lead, and, from the evidence of this lead infilling, dates the church as late as the fifteenth century. But it is equally possible that the letters were marked out by drill holes which were then connected with the chisel, and that the carver, pleased by the effect given by the sharp points of shadow in the drill holes, deliberately left them. The grooves do not seem suitable for retaining lead.
In the course of their history both churches were altered, even in Byzantine days. The south church is the earlier structure, but shows signs of several rebuildings. The irregular narthex and unsymmetrical eastern side chapels are evidently not parts of an original design. In the wall between the two churches there are indications which appear to show the character of these alterations and the order in which the different buildings were erected.
As has already been pointed out, the north side of the ambulatory in the south church, which for two-thirds of its